Bubble tube



FIG. 1 is a perspective view of a bubble tube showing my new design;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof, the left and right views being identicalto the front and rear views;

FIG. 4 is a top view thereof; and,

FIG. 5 is a bottom view thereof.

The ornamental design for a bubble tube, as shown and described.